This Program-Project in Liver Diseases represents a multidisciplinary program concerned with the following major projects. 1) The etiology, pathogenesis and treatment of viral hepatitis and of liver disease, both acute and chronic encountered in a high proportion of our renal transplant patients; 2) the potential genetic basis for postulated immunologic abnormalities that contribute to the development of chronic liver disease, using the chronic hepatitis B carrier as the initial focal point for assessment; 3) the immunologic function of Kupffer cells; 4) regulation of intermediary metabolism in liver, utilizing isolated liver cell preparations as an important experimental tool; and 5) hepatic transport function, with major emphasis concerned with sinusoidal uptake processes and canalicular excretory mechanisms.